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San Joaquin County <br /> 0P9uiti .c <br /> Environmental Health Department <br /> Z.•' �a� Z DIRECTOR <br /> Q 1868 East Hazelton Avenue Donna Heran, REHS <br /> X Stockton, California 95205-6232 PROGRAM COORDINATORS <br /> - — -- Robert McClellon, REHS <br /> C4� <br /> Jeff Carruesco, REHS, RDI <br /> F6 R�\P Website: www.Sjgov.Org/ehd Kasey Foley, REHS <br /> Phone: (209) 468-3420 Linda Turkatte, REHS <br /> Fax: (209)464-0138 Rodney Estrada, REHS <br /> Adrienne Ellsaesser, REHS <br /> November 13, 2014 <br /> Messrs. Kirk Larson, PG, and Robert Trommer, CHG <br /> State Water Resources Control Board <br /> Underground Storage Tank Cleanup Fund <br /> PO Box 944212 <br /> Sacramento CA 94244-2120 <br /> Subject: 701 Charter Way E., Stockton, CA <br /> Additional Rebound Monitoring Recommendation for CUF Claim No 12741 <br /> In accordance with Review Summary Report- Concur signed 22 April 2014 for the fifth annual <br /> review of the site by Kirk Larson and Robert Trommer of the State Water Resources Control <br /> Board (SWRCB) Cleanup Fund (Fund) for above-referenced site, the San Joaquin County <br /> Environmental Health Department (EHD) directed two rebound monitoring events before <br /> considering it for case closure. The Fund had concurred with EHD's recommendation for the <br /> rebound testing. <br /> Impacted soil and groundwater had been undergoing remediation through dual phase extraction <br /> (DPE). Since the vapor extraction portion of the system was initiated in January 2011, <br /> approximately 5,585 pounds of hydrocarbons had been recovered from subsurface soil, and <br /> approximately 407 pounds of dissolved contaminants had been recovered from groundwater at <br /> the time the DPE system was shut down 29 January 2014. The DPE system was shutdown at <br /> the direction of the EHD in response to the Fund's recommendation for case closure. <br /> Two post remediation groundwater monitoring events have been conducted since the DPE <br /> system shut down, the first on 28 May 2014, the second on 27 August 2014. Reports of findings <br /> have been submitted for both monitoring events. The EHD has evaluated the contaminant <br /> concentration trends in the monitoring wells and has determined that concentrations appear to <br /> be strongly rebounding in groundwater monitored by MW-1 and contaminant concentrations in <br /> groundwater monitored by MW-6 have been exhibiting a consistent increasing trend since April <br /> 2010 and indicate an unstable plume on the south margin of the site. With the exception of <br /> methyl tert-butyl ether (MTBE), contaminant concentrations in MW-6 are at their highest since <br /> monitoring of the well began in June 2009 — before DPE remediation was implemented. The <br /> plume is not assessed south of MW-6. <br /> The trends in MW-1 and MW-6 were neither noted nor commented on by the consultant, who <br /> recommended the site be considered for closure as a low risk groundwater site, the EHD <br /> strongly disagrees with that recommendation at this time. The EHD recommends that at a <br /> Additional Rebound Monitoring Recommendation for CUF Claim No 12741.doc <br />